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  1. /*
  2.  * MLP codec common code
  3.  * Copyright (c) 2007-2008 Ian Caulfield
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. #include <stdint.h>
  23.  
  24. #include "libavutil/crc.h"
  25. #include "libavutil/intreadwrite.h"
  26. #include "mlp.h"
  27.  
  28. const uint8_t ff_mlp_huffman_tables[3][18][2] = {
  29.     {    /* Huffman table 0, -7 - +10 */
  30.         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  31.         {0x04, 3}, {0x05, 3}, {0x06, 3}, {0x07, 3},
  32.         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  33.     }, { /* Huffman table 1, -7 - +8 */
  34.         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  35.         {0x02, 2}, {0x03, 2},
  36.         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  37.     }, { /* Huffman table 2, -7 - +7 */
  38.         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  39.         {0x01, 1},
  40.         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  41.     }
  42. };
  43.  
  44. static int crc_init = 0;
  45. #if CONFIG_SMALL
  46. #define CRC_TABLE_SIZE 257
  47. #else
  48. #define CRC_TABLE_SIZE 1024
  49. #endif
  50. static AVCRC crc_63[CRC_TABLE_SIZE];
  51. static AVCRC crc_1D[CRC_TABLE_SIZE];
  52. static AVCRC crc_2D[CRC_TABLE_SIZE];
  53.  
  54. av_cold void ff_mlp_init_crc(void)
  55. {
  56.     if (!crc_init) {
  57.         av_crc_init(crc_63, 0,  8,   0x63, sizeof(crc_63));
  58.         av_crc_init(crc_1D, 0,  8,   0x1D, sizeof(crc_1D));
  59.         av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
  60.         crc_init = 1;
  61.     }
  62. }
  63.  
  64. uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
  65. {
  66.     uint16_t crc;
  67.  
  68.     crc = av_crc(crc_2D, 0, buf, buf_size - 2);
  69.     crc ^= AV_RL16(buf + buf_size - 2);
  70.     return crc;
  71. }
  72.  
  73. uint8_t ff_mlp_checksum8(const uint8_t *buf, unsigned int buf_size)
  74. {
  75.     uint8_t checksum = av_crc(crc_63, 0x3c, buf, buf_size - 1); // crc_63[0xa2] == 0x3c
  76.     checksum ^= buf[buf_size-1];
  77.     return checksum;
  78. }
  79.  
  80. uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size)
  81. {
  82.     int i;
  83.     int num_bytes = (bit_size + 2) / 8;
  84.  
  85.     int crc = crc_1D[buf[0] & 0x3f];
  86.     crc = av_crc(crc_1D, crc, buf + 1, num_bytes - 2);
  87.     crc ^= buf[num_bytes - 1];
  88.  
  89.     for (i = 0; i < ((bit_size + 2) & 7); i++) {
  90.         crc <<= 1;
  91.         if (crc & 0x100)
  92.             crc ^= 0x11D;
  93.         crc ^= (buf[num_bytes] >> (7 - i)) & 1;
  94.     }
  95.  
  96.     return crc;
  97. }
  98.  
  99. uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size)
  100. {
  101.     uint32_t scratch = 0;
  102.     const uint8_t *buf_end = buf + buf_size;
  103.  
  104.     for (; ((intptr_t) buf & 3) && buf < buf_end; buf++)
  105.         scratch ^= *buf;
  106.     for (; buf < buf_end - 3; buf += 4)
  107.         scratch ^= *((const uint32_t*)buf);
  108.  
  109.     scratch = xor_32_to_8(scratch);
  110.  
  111.     for (; buf < buf_end; buf++)
  112.         scratch ^= *buf;
  113.  
  114.     return scratch;
  115. }
  116.